This invention relates to intake manifolds for internal combustion engines.
German Patent Gebrauchsmuster No. 89 14 049 discloses an intake manifold for an internal combustion engine in which the inner walls of individual intake pipes are formed by a separate part which is fitted into half-shells forming a manifold housing. The separate part can have a multi-part design, e.g. a design in which individual fitting parts are mounted together in the parting plane of the half-shells. This intake manifold is intended to provide economical manufacture and an improvement, which is not described in detail, resulting from smooth duct walls.
In such intake manifold arrangements, the seals between the inserted parts and the half-shells and between the individual inserted parts adjoining one another in the parting plane can present problems. Leaks occurring at these locations lead inevitably to losses in the volumetric efficiency in low to medium engine speed ranges requiring a high vacuum in the intake manifold.